Over the past two decades, unprecedented spruce beetle outbreaks have been observed throughout cordilleran North America. In contrast to historic spruce beetle outbreaks, recent outbreaks have not stemmed from clear, stand-level abiotic disturbance events, and instead, have been attributed to the progressive onset of climate change. With the continued influence of climate change, spruce beetle outbreak probabilities are expected to increase throughout the 21st century.
To provide insight for forest managers, this report summarizes the effect of climate change on spruce beetle ecology, population dynamics, and disturbance regimes. It also addresses the ecological forest management implications of altered spruce beetle disturbance regimes, and provides potential management responses for those managing spruce forests in a changing climate.
Spruce beetle disturbance is influenced both directly and indirectly by climate through changes in developmental timing, temperature-mediated population mortality, host-tree resistance, and trophic-level interactions. Spruce beetle outbreaks alter a suite of ecological forest values, and increased disturbance stands to fundamentally change the scope of these values in spruce-prevalent landscapes. Spruce beetle disturbance can influence stand structure and succession, wildfire, hydrology and aquatic ecosystems, wildlife, and forest carbon dynamics.
Direct and indirect control treatments used in conjunction with current forest inventories, effective spruce beetle monitoring programs, and strategic access development, provide forest managers with effective means to respond to increased spruce beetle disturbance within an integrated management framework. These treatments, however, are limited by economic, operational, and policy-driven constraints. Additionally, there are a number of harvesting considerations for spruce beetle that forest managers can incorporate into harvest planning.